Main Factors Controlling the Friction Coefficient of High Toughness Galvanized Bolts

The friction coefficient control of electro-galvanized high-toughness galvanized bolts needs to be carried out from two levels: the control of the characteristics of the bolt body and the control of the whole process of tightening. In order to better improve the tightening process, companies should create their own database of galvanized bolt friction and torque. According to the different diameters, pitch diameters, compressive strength grades, passivation layers, galvanized thicknesses and surface treatments of the joints, comprehensively carry out bolt tightening experiments to obtain the range of friction coefficients under different loads. In order to better set the detection range of the friction coefficient and control the consistency of the bolt friction coefficient, different bolts do not use the friction coefficient to finely manage and set the torque. For the control of the bolt body, among many factors, the passivation layer has a greater impact on the friction coefficient of the bolt. The reliability of controlling the passivation layer to improve the coefficient of friction of high toughness galvanized bolts is also the most significant. Accurate control of galvanized coatings is difficult. At the same time, passivation treatment is the final treatment of the bolt surface. In a whole process, if only the thickness of the passivation layer is controlled, it is difficult to control the passivation layer. To some extent, controlling the thickness of the passivation layer can make up for the insufficiency of the electroplating process layer. Therefore, the control of the friction coefficient of galvanized bolts should focus on the passivation treatment link, which can directly affect the accuracy of the control. The size of the coefficient of friction. According to the technology currently available, the friction coefficient of high-strength galvanized bolts treated with C-grade chromate is very different from that of electro-galvanized high-strength bolts treated with D-grade chromate. However, the range of friction coefficient of the same electro-galvanized high-strength bolts treated with chromate is relatively stable, and the range of friction coefficient of bolts treated with different chromates does not overlap. The friction coefficient range of C-grade chromate-treated galvanized bolts is 0.28 to 0.36, and the friction coefficient of D-grade chromate-treated galvanized bolts ranges from 0.18 to 0.25. Therefore, there is no difference between the passivation layers of electro-galvanized high-strength bolts at present. It is unreasonable to use the same torque to tighten the bolts treated with C-grade chromate and D-grade chromate, and it is also very bad to control the pre-tightening force.